Portable electronic devices such as smart phones, tablets, notebooks and other electronic devices have become an everyday need in the way we communicate and interact with others. The frequent use of these devices may require a significant amount of power, which may easily deplete the batteries attached to these devices. Therefore, a user is frequently needed to plug in the device to a power source, and recharge such device. This may require having to charge electronic equipment at least once a day, or in high-demand electronic devices more than once a day.
Such an activity may be tedious and may represent a burden to users. For example, a user may be required to carry chargers in case his electronic equipment is lacking power. In addition, users have to find available power sources to connect to. Lastly, users must plugin to a wall or other power supply to be able to charge his or her electronic device. However, such an activity may render electronic devices inoperable during charging.
Current solutions to this problem may include devices having rechargeable batteries. However, the aforementioned approach requires a user to carry around extra batteries, and also make sure that the extra set of batteries is charged. Solar-powered battery chargers are also known, however, solar cells are expensive, and a large array of solar cells may be required to charge a battery of any significant capacity. Other approaches involve a mat or pad that allows charging of a device without physically connecting a plug of the device to an electrical outlet, by using electromagnetic signals. In this case, the device still requires to be placed in a certain location for a period of time in order to be charged. Assuming a single source power transmission of electro-magnetic (EM) signal, an EM signal gets reduced by a factor proportional to 1/r2 in magnitude over a distance (r) in free space, in other words, it is attenuated proportional to the square of the distance. In most practical applications the attenuation is actually more severe than indicated by the inverse of the squared distance due to atmospheric conditions and other factors. Thus, the received power at a large distance from the EM transmitter is a small fraction of the power transmitted. To increase the power of the received signal, the transmission power would have to be boosted. Assuming that the transmitted signal has an efficient reception at three centimeters from the EM transmitter, receiving the same signal power over a useful distance of three meters would entail boosting the transmitted power by 10,000 times. Such power transmission is wasteful, as most of the energy would be transmitted and not received by the intended devices, it could be hazardous to living tissue, it would most likely interfere with most electronic devices in the immediate vicinity, and it may be dissipated as heat.
In yet another approach such as directional power transmission, it would generally require knowing the location of the device to be able to point the signal in the right direction to enhance the power transmission efficiency. However, even when the device is located, efficient transmission is not guaranteed due to reflections and interference of objects in the path or vicinity of the receiving device.